Sample preparation is a ubiquitous problem in biological analytical systems. The issue of providing sufficiently purified targets from diverse raw sample types to reliably perform downstream analytical assays is pervasive and covers cell biology, genomics, proteomics, metabolomics, food biology, molecular diagnostics, and many other biological and medical assays. While many advances in sample preparation have been made the chief solution has been to develop reagents that are used manually or in robotic systems that use rectilinear stages or multi-axis arms to manipulate samples.
Microfluidics and nanofluidics allow miniaturized sample volumes to be prepared for analysis. Advantages include the nanoscale consumption of reagents to reduce operating costs and full automation to eliminate operator variances. Microfluidic sample preparation can either interface with existing or future detection methods or be part of a completely integrated system. In the present application, methods and apparatuses are disclosed that integrate full volume sample preparation with volumes over 10 mL with microliter and smaller volumes for sample preparation and analysis.
Starting from the sample, the present invention can be applied to concentrate, and pre-separate components for further processing to detect and classify organisms in matrices comprising aerosol samples, water, liquids, blood, stools, nasal, buccal and other swabs, bodily fluids, environmental samples with analysis by ELISA, PCR or other nucleic acid amplification techniques, single molecule detection, protein arrays, mass spectroscopy, and other analytical methods well known to one skilled in the art.
Microfluidic nucleic acid purification can be performed to prepare the sample for nucleic acid assays. For DNA analysis, PCR amplification is one current method. Microarray DNA, RNA and protein analysis also requires extensive sample preparation before the sample can be applied to the microarray for reaction and readout.
Samples can be obtained by a wide variety of substrates and matrices. The matrix may contain complex mixtures including inhibitory compounds such as hemes, indigo, humic acids, divalent cations, and proteins etc that interfere with DNA-based amplification. Aerosols can contain large amounts of molds, metals, and soils humic and other acids that all interfere with PCR amplification—the gold standard.
Early work showed that as few as three seeded organisms could be detected from diluted samples of soil extracts followed by PCR amplification of two 16S ribosomal gene fragments. Low-melting-temperature agarose has been used to extract DNA from soil samples for 16S and 18S rDNA PCR amplification using universal primers. Spun separation gels in column format can be used, such as Sephadex columns. Multistep purifications such as organic extractions combined with Sephadex columns were developed. Bead beating was found to be an effective way to prepare samples for high numbers of organisms and grinding in liquid nitrogen to detect low numbers of organisms. While these methods are effective they were best suited for research laboratory environments.
Solid phase extractions to columns, beads, and surfaces can be used to purify DNA before DNA analysis. Proteinase K followed by a Qiagen QIA Amp silica-gel membrane columns and IsoCode Stix, an impregnated membrane-based technology, followed by heating, washing and a brief centrifugation were compared for B. anthracis Sterne vegetative cells in buffer, serum, and whole blood and spores in buffer and found to work well.
A variety of separations can be performed using the devices and methods of the invention. For example, the devices and methods of the invention can be used to perform chromatography, phase-based or magnetic-based separation, electrophoresis, distillation, extraction, and filtration. For example, a microfluidic channel or a capillary can be used for chromatography or electrophoresis. As well, beads, such as magnetic beads can be used for phase-based separations and magnetic-based separations. The beads, or any other surfaces described herein, can be functionalized with binding moieties that exhibit specific or non-specific binding to a target. The binding can be based on electrostatics, van der Walls interactions, hydrophobicity, hydrophilicity, hydrogen bonding, ionic interactions, as well as partially covalent interactions like those exhibited between gold and sulfur. In preferred embodiments, the devices and methods of the invention utilize immunomagnetic separations.
Immunomagnetic separation (IMS) is a powerful technology that allows targets to be captured and concentrated in a single step using a mechanistically simplified format that employs paramagnetic beads and a magnetic field (see Grodzinski P, Liu R, Yang J, Ward M D. Microfluidic system integration in sample preparation microchip-sets—a summary. Conf Proc IEEE Eng Med Biol Soc. 2004; 4:2615-8, Peoples M C, Karnes H T. Microfluidic immunoaffinity separations for bioanalysis. J Chromatogr B Analyt Technol Biomed Life Sci. 2007 Aug. 30, and Stevens K A, Jaykus L A. Bacterial separation and concentration from complex sample matrices: a review. Crit Rev Microbiol. 2004; 30(1):7-24). IMS can be used to capture, concentrate, and then purify specific target antigens, proteins, toxins, nucleic acids, cells, and spores. While IMS as originally used referred to using an antibody, we generalize its usage to include other specific affinity interactions including lectins, DNA-DNA, DNA-RNA, biotin-streptavidin, and other affinity interactions that are coupled to a solid phase. IMS works by binding a specific affinity reagent, typically an antibody or DNA, to paramagnetic beads which are only magnetic in the presence of an external magnetic field. The beads can be added to complex samples such as aerosols, liquids, bodily fluids, or food. After binding of the target to the affinity reagent (which itself is bound to the paramagnetic bead) the bead is captured by application of a magnetic field. Unbound or loosely bound material is removed by washing with compatible buffers, which purifies the target from other, unwanted materials in the original sample. Because beads are small (nm to um) and bind high levels of target, when the beads are concentrated by magnetic force they typically form bead beds of just nL-uL volumes, thus concentrating the target at the same time it is purified. The purified and concentrated targets can be conveniently transported, denatured, lysed or analyzed while on-bead, or eluted off bead for further sample preparation, or analysis.
Immunomagnetic separations are widely used for many applications including the detection of microorganisms in food, bodily fluids, and other matrices. Paramagnetic beads can be mixed and manipulated easily, and are adaptable to microscale and microfluidic applications. This technology provides an excellent solution to the macroscale-to-microscale interface: beads are an almost ideal vehicle to purify samples at the macroscale and then concentrate to the nanoscale (100's of nL) for introduction into microfluidic or nanofluidic platforms. Immunomagnetic separations are commonly used as an upstream purification step before real-time PCR, electrochemiluminescence, and magnetic force discrimination.
The ability to move fluids on microchips is a quite important. This invention describes technologies in sample capture and purification, micro-separations, micro-valves, -pumps, and -routers, nanofluidic control, and nano-scale biochemistry. A key component of the technology is Micro-robotic On-chip Valves (MOVe) technology (an example of which is shown in FIG. 1) and its application to miniaturize and automate complex workflows. Collectively the MOVe valves, pumps, and routers and the instrumentation to operate them can be referred to as a microchip fluid processing platform.
The heart of the microchip fluid processing platform technology are MOVe pumps, valves, and routers that transport, process, and enable analysis of samples. These novel externally actuated, pneumatically-driven, on-chip valves, pumps, and routers, originally developed in the Mathies laboratory at the University of California at Berkeley (U. C. Berkeley) (Grover, W. H. A. M. Skelley, C. N. Liu, E. T. Lagally, and R. M. Mathies. 2003. Sensors and Actuators B89:315-323; Richard A. Mathies et al., United States Patent Application, 20040209354 A1 Oct. 21, 2004; all of which are herein incorporated by reference in their entirety) can control fluidic flow at manipulate volumes from 20 nL to 10 μL.
The MOVe valves and pumps (FIG. 1) can combine two glass microfluidic layers with a polydimethyl siloxane (PDMS) deformable membrane layer that opens and closes the valve, and a pneumatic layer to deform the membrane and actuate the valve. The microfluidic channel etched in the top glass fluidic wafer is discontinuous and leads to vias through the “via wafer” and microfluidic channels to a valve seat which is normally closed (FIG. 1A). When a vacuum is applied to the pneumatic displacement chamber by conventional-scale vacuum and pressure sources, the normally closed PDMS membrane lifts from the valve seat to open the valve (FIG. 1B). The bottom panel of FIG. 1 shows a top view of the valve a similar scale as the other panels.
Three microvalves can be used to make a micropump on a microchip to move fluids from the Input area to the Output area on Microchip A. The fluids are moved by three or more valves. The valves can be created actuation of a deformable structure. In some implementations a valve seat is created and in other embodiments no valve seat may be needed. FIG. 2 shows MOVe devices from top to bottom: valve, router, mixer, bead capture. Self-priming MOVe pumps (FIG. 2, top) are made by coordinating the operation of three valves and can create flow in either direction. Routers are made from three or more MOVe valves (FIG. 2, top middle panel). Mixing has been a holy grail for microfluidics: MOVe mixers (FIG. 2, bottom middle panel) rapidly mix samples and reagents. MOVe devices work exquisitely with magnetic beads to pump or trap sets of beads (FIG. 2, bottom panel).
The normally closed MOVe valves, pumps, and routers are durable, easily fabricated at low cost, can operate in dense arrays, and have low dead volumes. Arrays of MOVe valves, pumps, and routers are readily fabricated on microchips. Significantly, all the MOVe valves, pumps, and routers on a microchip are created at the same time in a simple manufacturing process using a single sheet of PDMS membrane—it costs the same to make 5 MOVe micropumps on a microchip as to create 500. This innovative technology offers for the first time the ability to create complex micro- and nanofluidic circuits on microchips.
Patents and applications which discuss the use and design of microchips include U.S. Pat. No. 7,312,611, issued on Dec. 25, 2007; U.S. Pat. No. 6,190,616, issued on Feb. 20, 2001; U.S. Pat. No. 6,423,536, issued on Jul. 23, 2002; U.S. Ser. No. 10/633,171 Mar. 22, 2005; U.S. Pat. No. 6,870,185, issued on Mar. 22, 2005 US Application No. US 2001-0007641, filed on Jan. 25, 2001; US Application US20020110900, filed on Apr. 18, 2002; US patent application 20070248958, filed Sep. 15, 2005; US patent application US 20040209354, filed on Dec. 29, 2003; US patent application US2006/0073484, filed on Dec. 29, 2003; US20050287572, filed on May 25, 2005; US patent application US20070237686, filed on Mar. 21, 2007; US 20050224352 filed on Nov. 24, 2004; US 20070248958, filed on, Sep. 15, 2005; US 20080014576, filed on Feb. 2, 2007; and, US application US20070175756, filed on Jul. 26, 2006; all of which are herein incorporated by reference in their entirety.